Approx Reading Time-12In the age of post-truth, alternative facts and doctored images, we’re looking at how those of science use actual evidence for our greater benefit.


Welcome to The Science of Evidence, a six-part series which discusses what evidence is, how it is proved by science and how it underpins some of the most fundamental concepts in our society, such as decision making and the preservation of health.

A significant number of people do not understand what evidence actually is and blindly trust the “professionals” who are providing them advice, where the professionals have been taught to appreciate a belief backed up by supposed evidence. I say this as a note for later discussion.

As a scientist, you are often faced with trying to prove a hypothesis (a theory) and provide supporting evidence to your conclusions or to perhaps defend a thesis, but if you aren’t exposed to this in your daily life, you might read “supported by evidence” without thinking twice about critically appraising those who state that presented evidence is valid. So let’s investigate what evidence is and why it is so hard to come by, and discuss some of the debates that surround things in medicine, health and law, and other facets such as the quantification and valuation of saving somebody’s life or preserving their quality of life through investment in new medicines or health technology, with decision making based on evidence, and why some succeed where others fail.


What is evidence?

Evidence as defined by is:

1. That which tends to prove or disprove something; ground of belief; proof


2. Something that makes plain or clear; an indication or sign

This is a broad definition of evidence, so let’s break it down. The first definition, we will talk about within the concept of plain evidence. The second definition might be more appropriate to tackle when we talk about evidence within the law.

The first part of the definition is “That which tends to prove or disprove something”, where “that” is referring to information, which is generated by data. Data is everywhere and it is everything. Raw data however is useless to us. We can have a large amount of data collected over a long period but unless we somehow apply some concepts, measurements or statistics, it cannot be turned into information (which provides us with the very evidence that proves or disproves something).

In this series we will explore the generation of evidence using science (and its application to the broader society) to really drill down to the meaning of what scientific evidence is and to understand the claim “backed by science”, as well as why this applies a certain weight to a claim made by scientists, professional organisations, governments etc. We will also aim to explore the type of evidence that is required in a court, what happens when scientific evidence is presented in a court of law, and how findings of investigations are communicated.


The scientific methodology; proof by peer-review and consensus

Science and experiments are internationally comparable because they follow the same methodology (with some slight variation in technique). A methodology is an order of doing things that is reproducible to achieve the same or similar outcomes, kind of like making a cake; you know that if you add eggs, sugar, flour, butter and baking powder, stir together in a bowl then place in the oven at 150˚C for 30 or so minutes, it will result in the cake, and that this is reproducible.

The same thing happens in science, to achieve evidence instead of a cake. For example, if you want to know how fast a plant will grow in a week, we can do an experiment, where we take interval measurements, say perhaps twice a day, at 8am and 8pm – i.e., every 12 hours – giving us a starting point in time, then run the experiments for 7 days, which gives us 14 data points we can analyse to determine, using maths, how fast that plant grows in a week.

Science and experiments are internationally comparable because they follow the same scientific methodology, widely recognised internationally as the gold standard for experimentation to collect data for analysis to turn into evidence.

People might sometimes refer to observation. Given our plant experiment above, we observe the measurement using a ruler and record the value in centimetres (which also means our data is in centimetres). It is not that scientists see something once and record it; they observe it and critically analyse it. How can we critically analyse the above plant experiment? Well, we can know the total length the plant grows over the 7 days, by taking our first value and subtracting it from our final value. If we wanted to know on average the rate at which it grows, dividing it by the number of data points we have (14) will tell us how much the plant grows in a 12 hour interval (on average). No matter how complex the experiment, fundamentally this is what scientists are doing. The entire experiment however, is considered one data point to the greater community, so that is why we publish in peer-reviewed journals, which I will elaborate on below.

The scientific methodology is widely recognised internationally as the gold standard for experimentation to collect data for analysis to turn into evidence, and you can recognise this methodological approach through the heads that might be published in an academic journal, such as Hypothesis, Aim, Method, Results and Conclusion. More formally in academic journals there is usually a discussion section where the author tries to elaborate further on how they came to their conclusions. When publishing in journals they traditionally go through a peer-reviewed process, which is quite complex. Ultimately, when you submit a journal manuscript (the original unpublished article) to an editor of a journal, they then send it to people to be reviewed. The author is usually made anonymous and the peers are made anonymous to the author, so it is a blinded review by one expert on another expert’s work.

This is why evidence published in journals is so highly sought after. These journals are a source of truth the world over, and the reason we publish exactly how experiments are conducted is because it doesn’t matter what country you are in, the peer-review experts should be able to validate the results of the experiment by following the same techniques, given the same circumstance (i.e., the same type of plant and the same weather conditions, or if the plant was grown in a greenhouse etc.).

Sometimes, however, journals may be subject to inaccuracies, which we will talk about further when we discuss bias.


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